US4471910A - Diffuser with through-the-wall bleeding - Google Patents

Diffuser with through-the-wall bleeding Download PDF

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Publication number
US4471910A
US4471910A US06/337,890 US33789082A US4471910A US 4471910 A US4471910 A US 4471910A US 33789082 A US33789082 A US 33789082A US 4471910 A US4471910 A US 4471910A
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US
United States
Prior art keywords
wall
slot
diffuser
inlet
axis
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US06/337,890
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English (en)
Inventor
Michel V. de Paul
Gilbert Riollet
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Alsthom Atlantique SA
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Alsthom Atlantique SA
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Assigned to SOCIETE ANONYME DITE: ALSTHOM-ATLANTIQUE reassignment SOCIETE ANONYME DITE: ALSTHOM-ATLANTIQUE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: RIOLLET, GILBERT, VINCENT DE PAUL, MICHEL
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
    • F01D25/30—Exhaust heads, chambers, or the like
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
    • F04D29/68—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers
    • F04D29/681—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for elastic fluid pumps
    • F04D29/682—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for elastic fluid pumps by fluid extraction
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/40—Casings; Connections of working fluid
    • F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/44—Fluid-guiding means, e.g. diffusers
    • F04D29/441—Fluid-guiding means, e.g. diffusers especially adapted for elastic fluid pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2250/00—Geometry
    • F05D2250/70—Shape
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S415/00—Rotary kinetic fluid motors or pumps
    • Y10S415/914—Device to control boundary layer

Definitions

  • the present invention relates to a diffuser that is symmetrical about an axis AA' with a substantially axial inlet, and a flared outer wall leading from said inlet to an outlet. A proportion of the fluid flow inside the diffuser is bled off through said flared wall via a circular slot disposed symmetrically about the axis.
  • the fluid flows along the outer wall in the general inlet-to-outlet direction over the portion of the wall upstream from the bleed slot, but the flow downstream from the slot along said outer wall is reversed, i.e. it is from the outlet towards the bleed slot.
  • Preferred embodiments of the present invention enable such separation to be avoided.
  • the present invention provides a diffuser with through the wall bleeding, said diffuser being symmetrical about an axis AA', and comprising a fluid inlet on said axis, a flared outer wall leading from said fluid inlet to a fluid outlet, and a circular bleed slot arranged symmetrically about said axis AA' in the flared portion of said outer wall, thereby dividing said outer wall into an upstream portion and a downstream portion.
  • Said flared outer wall has a profile such that, in operation, the direction of fluid flow along the surface of said wall is from said inlet towards said outlet, both over the upstream portion of said wall and over he downstream portion of said wall, and wherein the pressure gradient along said wall in said direction of fluid flow and as measured at the surface of said wall is negative upstream from said slot and positive downstream therefrom.
  • Diffusers are also known in which the pressure gradient on both sides of the slot is nil.
  • said slot has an entry angle lying between 100° and 120° as measured from the flow direction along the axis AA'.
  • S 0 is the inlet cross section of the diffuser
  • r is the radial distance between the slot and the axis
  • V 0 is the average fluid speed in the inlet cross section of the diffuser
  • V 1 is the fluid speed over the upstream portion of the outer wall at the inlet to the slot.
  • R 1 is the radius of curvature of the upstream portion of the outer wall at the inlet to the slot.
  • the optimum slot width is close to the value given by the equation. If the slot is too narrow, then its chances of capturing possible separation zones upstream from the slot are reduced, while losses at the slot are increased for constant bleed ratio since the entry speed into the slot must be increased. On the other hand, if the slot is too wide, the entry speed into the slot for given bleed ratio becomes too low thereby favouring separation upstream from the slot, while increasing the speed against the leading edge of the downstream portion of the wall, thereby thickening the boundary layer, maybe up to the point of separation.
  • the invention is particularly effective when the outlet angle from the diffuser is about 90°, i.e. when the diffuser is a radial diffuser.
  • FIG. 1 is a schematic section which shows a first, or desired type of flow in a diffuser having an axial inlet an a bleed slot in the flared portion of the outer wall;
  • FIG. 2 is a similar schematic view to that of FIG. 1 which shows a second, or undesired type of flow in the same diffuser as shown in FIG. 1;
  • FIG. 3 is a cross section through a diffuser in accordance with the present invention.
  • FIG. 4 is a cross section through the slot entrance of FIG. 3, showing the region marked IV, to a larger scale;
  • FIGS. 5 to 8 are graphs showing how the bleed ratio varies as a function of slot width.
  • FIG. 9 is a graph showing the variation of fluid speed along the outer wall of the diffuser.
  • FIGS. 1 and 2 show a conventional axial inlet diffuser having a flared outer wall divided by a slot 1 into an upstream portion 2 and a downstream portion 3.
  • the diffuser also has an inner wall 4.
  • the diffuser is symmetrical about an axis AA', and the profile of the outer wall 2, 3 is such that the pressure gradient upstream and downstream from the slot is nill.
  • FIG. 1 shows the desired normal flow.
  • the boundary layer upstream from the slot 1 along the upstream portion 2 of the outer wall is sucked into the slot 1.
  • FIG. 5 is a graph showing the bleed ratio X as a function of the width b of the slot 1.
  • a first, dot-dashed curve (I) shows minimum values of X as a function of b to be sure of establishing the flow pattern shown in FIG. 1, while a second, continuous, curve (II) shows maximum values of X as a function of b to be sure of establishing the flow pattern shown in FIG. 2.
  • b 0 of b there are two corresponding values of X: X 1 on the curve I and X 2 on the curve II.
  • X less than or equal to X 2 the FIG. 2 flow pattern will always occur.
  • FIG. 3 shows a diffuser in accordance with the invention. It is symmetrical about the axis AA'.
  • the outer wall has a slot 1 dividing it into an upstream portion 2 and a downstream portion 3.
  • the profile of the outer wall is such that the pressure gradient measured along its surface in the direction of fluid flow is negative upstream from the slot and positive downstream therefrom.
  • the inlet cross section of the diffuser is S 0 and the average speed of fluid flow at this point is V 0 .
  • the slot 1 is circular and is also symmetrical about the axis AA'. Its inlet BC is of width b and the speed of fluid flow along the wall 2 at point C of the inlet to the slot 1 is V 1 .
  • the slot 1 flares slightly downstream from its inlet.
  • the slot 1 is at an angle ⁇ to the axis AA'.
  • FIG. 6 shows the curves I and II for a diffuser in accordance with the invention, i.e. in which the profile of the outer wall is such that the pressure gradient in the direction of fluid flow measured at its surface is negative upstream from the slot and positive downstream therefrom.
  • Curves I and II are both lower than in FIG. 5, and it is therefore possible to obtain proper operation at a considerably lower bleed ratio for any given value of slot width b.
  • the pressure along the upstream wall portion 2 decreases progressively from the inlet to the diffuser up to the slot 1, whereby the fluid is accelerated and the boundary layer will be kept in a state far removed from separation. Nonetheless, too high a speed at the inlet to the diffuser must be avoided since that would lead high losses in the slot, and possibly to compressibility problems.
  • the chosen slot entry speed will lie in the range 15% to 40% faster than the speed of entry into the diffuser.
  • the profile of the downstream wall portion 3 reduces the risk of the FIG. 2 flow pattern forming.
  • the variation of pressure along the inner wall 4 of the diffuser depends on the deflection required for a given diffuser.
  • the inlet angle ⁇ of the slot 1 relative to the axis AA' is chosen to lie in the range 100° to 120°, thereby reducing the minimum bleed ratios of curve I (see FIG. 7).
  • the width of the slot is an important parameter. If the slot is too narrow, there is less chance of capturing a boundary layer that has become separated from the upstream wall portion 2. Also, slot losses are increased (for constant bleed ratio). If the slot is too wide, separation along the upstream wall portion 2 is encouraged, and further, the stop point S (i.e. where the flow speed is nil) may move a small way into the slot, which leads to excessively high flow speeds going round the leading edge following the point S on the upstream wall portion 3. This leads to the boundary layer on the wall portion 3 being increased in thickness, hence increasing the danger of its becoming separated with consequent increase in diffuser losses.
  • the ratio V 1 /V 0 is easy to measure by placing a first static pressure probe in the slot inlet (p1), a second in the diffuser inlet plane (p0), and pitot tube in said inlet plane to measure the stop pessure (p0*).
  • the ratio V 1 /V 0 is then equal to: ##EQU4##
  • FIG. 9 shows the variation in the ratio V/V 0 (where V is the speed at a point M on the upstream or the downstream wall portion 2, 3) as a function of the curvilinear distance along the curve 0M, where 0 is the point on the upstream wall portion 2 at the inlet to the diffuser.
  • the downstream wall portion 3 is offset in the flow direction (see FIG. 4) by a distance ⁇ defined as the distance between two planes perpendicular to the axis AA'; the first, or upstream plane is the plane tangential to the upstream wall portion 2, and the second, or downstream plane is the plane passing through the centre of the circular cross section of the upstream tip of the downstream wall portion 3.
  • the offset distance ⁇ is preferably equal to or slightly greater than the optimum slot width b opt mentioned earlier.
  • the curve I becomes practically the same as the curve II (see FIG. 8), with the minimum valve of said curves occurring when the width of the slot is equal or near to b opt .
  • the profile of the leading edge of the downstream wall portion 3 is preferably chosen so that the radius of the cicular cross section of its upstream tip is equal to or greater than b opt /4.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
  • Jet Pumps And Other Pumps (AREA)
  • Aerodynamic Tests, Hydrodynamic Tests, Wind Tunnels, And Water Tanks (AREA)
  • Medicines That Contain Protein Lipid Enzymes And Other Medicines (AREA)
  • External Artificial Organs (AREA)
  • Soil Working Implements (AREA)
  • Percussion Or Vibration Massage (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)
  • Medicinal Preparation (AREA)
  • Absorbent Articles And Supports Therefor (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
  • Finger-Pressure Massage (AREA)
  • Walking Sticks, Umbrellas, And Fans (AREA)
  • Catching Or Destruction (AREA)
US06/337,890 1981-01-08 1982-01-07 Diffuser with through-the-wall bleeding Expired - Lifetime US4471910A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8100210 1981-01-08
FR8100210A FR2497544A1 (fr) 1981-01-08 1981-01-08 Diffuseur a aspiration parietale

Publications (1)

Publication Number Publication Date
US4471910A true US4471910A (en) 1984-09-18

Family

ID=9253948

Family Applications (1)

Application Number Title Priority Date Filing Date
US06/337,890 Expired - Lifetime US4471910A (en) 1981-01-08 1982-01-07 Diffuser with through-the-wall bleeding

Country Status (13)

Country Link
US (1) US4471910A (pt)
EP (1) EP0056233B1 (pt)
JP (1) JPS57146003A (pt)
KR (1) KR890000914B1 (pt)
AT (1) ATE9832T1 (pt)
AU (1) AU547535B2 (pt)
BR (1) BR8200051A (pt)
CA (1) CA1193513A (pt)
DE (1) DE3260910D1 (pt)
ES (1) ES8302862A1 (pt)
FR (1) FR2497544A1 (pt)
RO (1) RO82608A (pt)
ZA (1) ZA82121B (pt)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5059093A (en) * 1990-06-07 1991-10-22 United Technologies Corporation Compressor bleed port
EP1329595A1 (fr) * 2002-01-22 2003-07-23 Snecma Moteurs Diffuseur pour moteur à turbine à gaz terrestre ou aèronautique
US20040244379A1 (en) * 2002-12-17 2004-12-09 Walker Alastair D. Diffuser arrangement
US20130051974A1 (en) * 2011-08-25 2013-02-28 Honeywell International Inc. Gas turbine engines and methods for cooling components thereof with mid-impeller bleed cooling air
US8893511B2 (en) 2009-07-24 2014-11-25 General Electric Company Systems and methods for a gas turbine combustor having a bleed duct
CN103244459B (zh) * 2013-04-25 2015-08-05 哈尔滨工业大学 一种亚音速吸附式轴流压气机气动设计方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8381532B2 (en) * 2010-01-27 2013-02-26 General Electric Company Bled diffuser fed secondary combustion system for gas turbines

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR992353A (fr) * 1944-06-22 1951-10-17 Cem Comp Electro Mec Amélioration de la récupération des diffuseurs
GB1000767A (en) * 1963-05-08 1965-08-11 Int Research & Dev Co Ltd Diffusers for fluids
GB1024328A (en) * 1961-12-05 1966-03-30 Gen Electric Improvements in high performance fluid-dynamic component
US4214452A (en) * 1977-08-25 1980-07-29 Alsthom-Atlantique Exhaust device for a condensable-fluid axial-flow turbine

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR992353A (fr) * 1944-06-22 1951-10-17 Cem Comp Electro Mec Amélioration de la récupération des diffuseurs
GB1024328A (en) * 1961-12-05 1966-03-30 Gen Electric Improvements in high performance fluid-dynamic component
GB1000767A (en) * 1963-05-08 1965-08-11 Int Research & Dev Co Ltd Diffusers for fluids
US4214452A (en) * 1977-08-25 1980-07-29 Alsthom-Atlantique Exhaust device for a condensable-fluid axial-flow turbine

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5059093A (en) * 1990-06-07 1991-10-22 United Technologies Corporation Compressor bleed port
EP1329595A1 (fr) * 2002-01-22 2003-07-23 Snecma Moteurs Diffuseur pour moteur à turbine à gaz terrestre ou aèronautique
US20040244379A1 (en) * 2002-12-17 2004-12-09 Walker Alastair D. Diffuser arrangement
US7062918B2 (en) * 2002-12-17 2006-06-20 Rolls-Royce Plc Diffuser arrangement
US8893511B2 (en) 2009-07-24 2014-11-25 General Electric Company Systems and methods for a gas turbine combustor having a bleed duct
US20130051974A1 (en) * 2011-08-25 2013-02-28 Honeywell International Inc. Gas turbine engines and methods for cooling components thereof with mid-impeller bleed cooling air
CN103244459B (zh) * 2013-04-25 2015-08-05 哈尔滨工业大学 一种亚音速吸附式轴流压气机气动设计方法

Also Published As

Publication number Publication date
EP0056233A1 (fr) 1982-07-21
CA1193513A (fr) 1985-09-17
FR2497544B1 (pt) 1985-05-03
KR890000914B1 (ko) 1989-04-13
AU7926482A (en) 1982-07-15
JPH0259285B2 (pt) 1990-12-12
EP0056233B1 (fr) 1984-10-10
RO82608A (ro) 1983-09-26
KR830009415A (ko) 1983-12-21
DE3260910D1 (en) 1984-11-15
FR2497544A1 (fr) 1982-07-09
ZA82121B (en) 1982-11-24
ES508555A0 (es) 1982-12-01
AU547535B2 (en) 1985-10-24
BR8200051A (pt) 1982-10-26
JPS57146003A (en) 1982-09-09
ATE9832T1 (de) 1984-10-15
ES8302862A1 (es) 1982-12-01

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